1. Field of the Invention
This invention relates to refrigerators and, more specifically, to thermoacoustic refrigeration pumps.
2. Description of the Related Art
Over the past thirteen years, there has been an increasing interest in the development of thermoacoustical cooling engines (pumps) for a variety of commercial, military, and industrial applications. Interest in thermoacoustic cooling has escalated rapidly with the production ban of chlorofluorocarbons (CFCs) which will be imposed worldwide at the end of 1995. The increased interest in thermoacoustic cooling is due to the fact that thermoacoustic refrigeration can be accomplished by using only inert gases which are nontoxic and, in addition, do not contribute to stratospheric ozone depletion nor to global warming.
Prior to the present invention, electrically driven thermoacoustic engines had been optimized for scientific research purposes, but were only capable of providing a few Watts of useful cooling. See S. L. Garrett, J. A. Adeff and T. J. Hofler, "Thermoacoustic Refrigerator for Space Applications," Journal of Thermophysics and Heat Transfer, Vol 7, No. 4, pp. 595-599 (1993). Earlier designs, see T. J. Hofler, I. C. Wheatly, G. W. Swift, and A. Migliori, "Acoustic Cooling Engine," U.S. Pat. No. 4,722,201 to T. J. Hofler, et al., and see Garrett, et al. above, typically incorporated a one-quarter wavelength resonator driven by a single loudspeaker at one end and containing a single stack and one pair of primary heat exchangers in close proximity to either end of the stack.
For the large heat loads required in this high-powered thermoacoustic refrigerator, the heat exchangers from earlier thermoacoustic refrigerators, U.S. Pat. No. 4,722,201 and see S. L. Garrett et al., "Thermoacoustic Refrigeration for Space Applications," Journal of Thermophysics and Heat Transfer, Vol 7, No 4, pp 595-599 (1993), which relied on thermal conduction through solid metal, were grossly inadequate. The high-powered thermoacoustic refrigerator described in this specification uses a novel gas-to-liquid heat exchanger which is capable of transporting hundreds of Watts of heat to and from the stack. See: S. L. Garrett, "Thermoacoustic Life Sciences Refrigerator: Heat Exchanger Design and Performance Prediction." unpublished technical report, June 1992, and S. L. Garrett, D. K. Perkins and A. Gopinath, "Thermoacoustic Refrigerator Heat Exchangers: Design, Analysis and Fabrication," Heat Transfer 1994, proceedings of the Tenth International Heat Transfer Conference, Vol 4, pp 375-380 (Aug. 1994).